System for liquid extraction, and methods

ABSTRACT

A process for removing water from solid material using liquid-solid extraction and liquid-liquid extraction. In most embodiments, multiple solvents are used to remove the water from the solids and obtain dry solids. Multiple solvents facilitate the removal of the water from the solids, by replacing the water with a solvent, replacing that solvent with a different solvent, and then eventually removing the second solvent from the solids. The process utilizes a lesser amount of thermal energy to dry the solids and separate the solvents than conventionally used in drying processes. The first solvent selected has a lower heat of vaporization, enthalphy of vaporization, boiling point, or other such physical property, than water. Each additional solvent can have a still lower heat of vaporization, enthalphy of vaporization, boiling point, or other such physical property.

This application is a continuation-in-part of co-pending U.S.application Ser. No. 10/538,557, filed Jan. 6, 2006. The entiredisclosure of application Ser. No. 10/538,557 is incorporated herein byreference.

FIELD OF THE INVENTION

The invention is directed to a system, and its methods of use, forextracting liquid water and/or a hydrocarbon from a feed stream using atleast two solvents. The system and method can generally be described asa reduced energy extraction and drying processes.

BACKGROUND OF THE INVENTION

For many processes, an exiting stream, whether considered a wastestream, a by-product, or the main desired stream, is composed of a solidmaterial wet with water. This water is typically found in both theinterstitial spaces of the solid and is absorbed or adsorbed by thesolid. Water such as this has typically been removed by drying thesolids with thermal energy. This process generally requires a largeamount of heat or energy to remove the water from the solids and obtaindry, usable solids.

Attempts have been made to use organic solvents to remove water from wetsolids using solvents such as hexane. Essentially, the hexane is used todisplace the water from the solids. The hexane remaining with the solidsis then evaporated from the solids with thermal energy. Again, thisprocess generally requires a large amount of thermal energy, but lessthan if water alone was being dried from the solids. However hexane alsobrings with it certain other concerns, such as toxicity. Further,because of poor displacement, large amounts of residual water may remainwith the solids.

Some examples of known extraction methods include Baird, U.S. Pat. No.4,251,231, which utilizes liquid-liquid extraction to directly extractalcohol suitable for use in gasohol from a fermentation mixture.Gasoline was used as the extraction solvent. The water was removed byeither the use of adsorbents or absorbents, or by chilling the extractedalcohol-gasoline product to a temperature below about −10° F., therebyremoving the water.

During the ethanol manufacturing process, solids, wet with primarilywater and some ethanol, exit the fermentation process as a beer stream.Other materials, such as oils and glycerol are also present in the beerstream. It is desired to obtain individual output streams of dry solids,water, and ethanol.

The beer stream solids, as discussed above, have the water in both theinterstitial spaces of the solid and that which is absorbed or adsorbedby the solid. This water, and any ethanol, has typically been removed bydrying the solids with thermal energy. Preferably, the ethanol isrecovered and is used; unfortunately, recovery of pure, or fairly pureethanol, is not usual. Additionally, preferably the water issufficiently pure that the water can be readily disposed; unfortunately,the water has contaminants that inhibit direct, unmanaged disposal.Still further, contaminants, such as oils and glycerol, remain in thesolids, making them undesirable for many applications.

What is needed is a low cost, more heat or energy efficient process fordrying solids wet with water. It would be beneficial if the variousoutput streams from the process could be reclaimed and used.

SUMMARY OF THE INVENTION

The invention is a process for separating water from solids and fromother hydrocarbons that may be present, the process utilizing at least20% less energy than conventional forced air drying of the samematerial.

Solids, wetted with water, are separated from the water and dried by theinventive process. The process removes the water residing in theinterstitial spaces of the solids, as well as some of the water that hasbeen absorbed by the solids. The process uses a liquid-solid extractionprocess to remove the water from the solid feed stream.

In one embodiment, multiple solvents are used to step-wise remove thewater from the solids and obtain dry solids. The multiple solventsfacilitate the removal of the water from the solids, by step-wisereplacing the water with a solvent, replacing that solvent with afurther solvent, and then eventually removing the further solvent fromthe solids.

In another embodiment, multiple solvents are combined and used in singlestep to remove the water from the solids and obtain dry solids. Thecombined multiple solvents facilitate the removal of the water from thesolids, by replacing the water with one of the solvents, replacing thatsolvent with a further solvent, and then eventually removing the furthersolvent from the solids. In this embodiment, the two (or more) solventsare introduced to the solids concurrently or simultaneously, preferablymixed together.

Use of multiple solvents, whether applied sequentially or concurrently,facilitates the separation of the water from the solids, the solventsfrom the water, and the various solvents from each other. The multiplesolvents are separated from each other by liquid-liquid extraction ordistillation processes.

Multiple solvents utilize less thermal energy to dry the solids andseparate the solvents than conventionally used in drying processes. Atleast one solvent selected has a lower heat of vaporization, enthalpy ofvaporization, boiling point, or other such physical property, thanwater. Each additional solvent has a lower heat of vaporization,enthalpy of vaporization, boiling point, or other such physical propertythan the first solvent used. These general properties apply whether thesolvents are used sequentially (e.g., step-wise) or concurrently (e.g.,mixed together).

In a further embodiment, the invention is directed to a process fordrying solids initially wet with water. The process includes contactinga feed stream comprising solids having interstitial spaces, and waterpresent in the interstitial spaces, with a solvent. This solvent may bea combination of two or more solvents. The water present in theinterstitial spaces is displaced by the solvent, leaving the solvent inthe interstitial spaces. The feed stream having the solvent in theinterstitial spaces can then be contacted with a second solvent; and thefirst solvent present in the interstitial spaces is displaced by thesecond solvent, thus providing the second solvent in the interstitialspaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a general process according to thepresent invention, having an ‘initial’ separation subprocess, a‘solvent-from-solids’ separation subprocess and a ‘water-from-solvents’separation subprocess.

FIG. 2 is a schematic process diagram of a general, first embodiment ofthe ‘introductory’ separation subprocess according to the presentinvention.

FIG. 3A is a schematic diagram of an extraction unit of the subprocessof FIG. 2;

FIG. 3B is an enlarged, perspective view of a portion of the extractionunit of FIG. 3A;

FIG. 4 is a schematic process diagram of a first embodiment of the‘solvent-from-solids’ separation subprocess according to the presentinvention;

FIG. 5 is a schematic process diagram of a portion of the‘solvent-from-solids’ separation subprocess of FIG. 4.

FIG. 6 is a schematic process diagram of a first embodiment of the‘water-from-solvents’ separation subprocess according to the presentinvention.

FIG. 7 is a schematic process diagram of a preferred process accordingto the present invention.

FIG. 8 is a schematic diagram of an alternate process according to thepresent invention.

FIG. 9 is a schematic diagram of another alternate process according tothe present invention.

FIG. 10 is a schematic diagram of yet another alternate processaccording to the present invention.

FIG. 11 is a binary diagram for a preferred three-solvent systemaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As provided above, the invention is directed to processes for separatingwater from solids by utilizing at least two solvents. The at least twosolvents can be applied to the solids either sequentially or step-wise(i.e., one after the other), or mixed together.

The process uses a first solvent to displace the water from theinterstitial spaces in the solids. This first solvent, having a lowerheat of vaporization and boiling point than the water, is easier toremove from the solids than water. A second solvent is used to displacethe first solvent from the solids. The second solvent has a lower heatof vaporization and boiling point than the first solvent. The secondsolvent can be introduced to the solids subsequent to introducing thefirst solvent, or concurrent with the first solvent.

The first solvent is preferably soluble in water but does not form anazeotropic mixture with water. An azeotropic mixture is a mixture of twoor more substances that behaves like a single substance. The vaporproduced by partial evaporation of the liquid has the same compositionas the liquid; that is, vaporization of the mixture does not result inseparation of the initial substances.

The second solvent is preferably soluble with the first solvent butinsoluble with water. Depending on the solvents used and their ratios,the first and second solvents may or may not form an azeotropic mixture.The second solvent may, however, be miscible with the first solvent,and/or with water.

Any additional or subsequent solvent(s) can be soluble with thepredecessor solvent, and may or may not form an azeotropic mixture withthe other solvents.

By utilizing this multiple solvent, liquid-extraction process, theenergy needed to dry the solids and separate the various solvents fromeach other and from water is greatly reduced compared to conventionalprocesses.

The processes of the invention can generally be reduced to an initialextraction subprocess that removes water from the solids followed by twosubprocesses, a ‘solvent-from-solids’ separation subprocess whichseparates solvent from the solids, and a ‘water-from-solvents’separation subprocess that separates and reclaims the water andsolvents, and optionally, other components.

Referring now to the figures, a diagrammatic rendering of a processaccording to the present invention, using two sequentially appliedsolvents, is generally depicted in FIG. 1. This process has an initialseparation process 100 to separate water from the solids and two generalsubprocesses, one for removing solvent from solids, subprocess A, and asecond for separating and reclaiming water and solvents, subprocess B.

Feed stream 10, an aqueous stream with solids therein, is illustratedentering the system at the top left corner of FIG. 1. The type andamount of solids in stream 10 will vary. The specific solids presentwill depend on the source, and example sources include grains, otherplant materials and earthen materials.

The amount of solids in stream 10 is generally 5 to 50% by weight. Acommon amount of solids in stream 10 is about 10-12%. As mentioned,steam 10 is typically an aqueous stream, with the water present at alevel of about generally 50 to 95% by weight. A common amount of waterin stream 10 is about 78 wt-%. Other liquids, in addition to the water,can be and are often present in feed stream 10.

If feed stream 10 is from a fermentation process, stream 10 generallyincludes alcohol (such as ethanol). The level of alcohol and othercomponents in stream 10 is dependent on the efficiency of the processproviding stream 10, however, the alcohol in stream 10 is generally lessthan 16 wt-%. Usually, the level of alcohol in stream 10 is greater thanabout 8 wt-%. A common level of alcohol in some streams is about 15wt-%.

Other materials are typically present in stream 10. For example, oil(such as corn oil) and glycerol are usually present. Examples of solutesthat may be present include acids (such as acetic acid), aldehydes (suchas acetaldehyde), and various sugars. The levels of these material arelow, typically less than 2 wt-% and often less than 1 wt-% of stream 10.

Returning to FIG. 1, feed stream 10 is fed into a water/solid extractionsystem 100 where the solids of feed stream 10 are separated from water.An alternate descriptive term for water/solid extraction system 100 is awater extractor or a solid-liquid extraction unit. Extraction system 100is configured to remove water from feed stream 10 and replace the waterwith a solvent. Additional details regarding a preferred extractionsystem 100 are provided below.

Extraction system 100 transfers one or more components from feed stream10 into the extraction solvent stream (described below). Typically,extraction system 100 operates in a counter-current arrangement; thatis, the extraction solvent stream enters system 100 farthest from wherefeed stream 10 enters, and the two streams contact and passcounter-currently to each other.

In addition to feed stream 10 being fed into extraction system 100, anextraction solvent stream 15 is fed into system 100. It is the solventin stream 15 that will extract and replace the water from feed stream10. First solvent from stream 15 combines with or displaces the originalaqueous liquids from feed stream 10 as feed stream 10 and solvent stream15 pass in system 100.

This exchange of one solvent for another in a stream is due toconcentration equilibrium. Solvent, present at a high concentration instream 15, moves to a stream having a lower concentration, i.e., stream10; likewise, water, present at a high concentration in stream 10, movesto a stream with a lower concentration of water, i.e., stream 15.

The solvent is selected for stream 15 based on a lower heat ofvaporization or enthalpy of vaporization than the water in feed stream10. Water has a heat of vaporization of 1000 BTU per pound of water,thus, solvent of stream 15 should have a heat of vaporization less than1000. The lower the heat of vaporization in relation to 1000 BTU, theeasier the subsequent separation of solvent 15 from water. The solventof stream 15 can be water soluble. The solvent of stream 15 and watermay or may not form an azeotropic mixture. If an azeotrope is notformed, subsequent separation of the solvent and water is simple.

Although virtually any water soluble solvent can be selected forextraction solvent stream 15, it is preferred to select one which mayalready be present in feed stream 10. Examples of suitable solventsinclude alcohols (such as ethanol, methanol, isopropyl alcohol, andgasohol) and ketones (such as acetone, methyl ethyl ketone (MEK), methylisobutyl ketone (MIBK)), and mixtures thereof. If feed stream 10 isprimarily composed of solids, water and alcohol, as it is from manyfermentation processes, solvent stream 15 is preferably an alcohol, forexample, the alcohol that is present in feed stream 10.

As stated above, water in feed stream 10 is replaced with first solventfrom stream 15 by water extraction system 100. The resulting outputstreams from system 100 are solids stream 20 and liquid stream 30.

Solid stream 20 is a wet solids stream, composed of the solids fromstream 10 and an amount of first solvent from stream 15. Wet solidsstream 20 progresses to and is treated by subprocess A, as will bedescribed below. Liquid stream 30 is generally composed of the originalliquid from feed stream 10 (that is, the water and any other liquid,such as an alcohol) and the solvent from solvent stream 15. Liquidstream 30 progresses to and is treated by subprocess B, described below.

Extraction System 100

A preferred configuration for a water-solid extraction system 100 isillustrated in FIG. 2. As seen in FIG. 1 and in FIG. 2, feed stream 10and solvent stream 15 enter system 100, and wet solids stream 20 andliquid stream 30 exit system 100.

Water-solid extraction system 100 has at least one extraction unit 110.In the system 100 illustrated in FIG. 2, system 100 has three extractionunits, specifically, 110A, 110B, 110C. Each extraction unit 110 includesa mixing tank 112, a pump 114, mechanical separator 116, and the pipingto operably connect the elements.

Mixing tank 112 can be any suitable receptacle for combining andtemporarily storing solid and liquid materials. In the embodimentillustrated, tank 112 accepts beer feed 10 and water/solvent stream 31,which will be described below. Examples of suitable materials for tank112 include steels, such as carbon steel and stainless steels. Apreferred material is 304 stainless steel. The volume of tank 112 isbased on the material flow volumes and desired residence time in tank112. A 30 gallon tank is a suitable size for some processes.

Pump 114, used to move material from tank 112, is positioned downstreamof tank 112. Pump 114 is selected for its ability to move the materialfrom tank 112, which includes solid material and liquid, to mechanicalseparator 116. Examples of suitable pumps include diaphragm pumps,centrifugal pumps, and pumps designed to pump a combination of liquidand solids. An example of a preferred pump 114 is a centrifugal pumpavailable from Goulds Pumps of ITT Industries.

Mechanical separator 116 separates solid material from liquid. Examplesof suitable mechanism separating equipment include Rotocel extractors,double screw extractors, baskets, rotary perforated belts, slidingrolls, and loop extractors; this equipment is well known forsolid/liquid extraction processes. The specific equipment used will bedependent on the solvents used in the process and in the solvent ratios.Preferred equipment for use in extraction system 100 is a stationaryscreen, described below.

The piping connecting tank 112, pump 114, and mechanical separator 116,for each extraction unit 110, is selected for its ability to move thesolid-liquid material. An example of preferred piping is 1 inch carbonsteel piping.

A preferred configuration for a screen mechanical separator 116 isillustrated in FIG. 3A. Separator 116 has a housing 1162 in which is ascreen 1163. Screen 1163 has a first, curved portion 1163A and a second,generally vertical portion 1163B. Screen 1163 separates housing 1162into a filtrate side 1167 and a cake side 1168.

A nozzle 1164 is present to spray wet solids stream 11, from tank 112,onto screen 1163. In one preferred process configuration, nozzle 1164 isconfigured to provide a flow of 8-10 gallons/minute of wet solids stream11 onto screen 1163.

An enlargement of screen 1163 is illustrated in FIG. 3B. Screen 1163 hasa plurality of separating members 1165 secured by cross-members 1166,both of which can be carbon steel or stainless steel. Separating members1165, positioned closer to nozzle 1164, on cake side 1168, preferablyextend vertically, to facilitate solids running down members 1165. Inone preferred process, members 1165 and 1166 are arranged to provide amesh size (i.e., an opening) of at least 0.01 inch.

Wet solids stream 11, sprayed by nozzle 1164 primarily onto curvedportion 1163A, is separated by members 1165 and 1166. Liquid from stream11 passes through screen 1163 and is collected on filtrate side 1167.The solids, too large to pass through screen 1163, remain on cake side1168.

It is understood that some liquid will not pass through screen 1163 butwill remain with the solids. Screen 1163 may have a dam or baffle 1169positioned at or near the juncture of curved portion 1163A and verticalportion 1163B, to retain solids in an attempt to have liquid droptherefrom.

The liquid, having passed through screen 1163 to filtrate side 1167,would be removed from housing 1162 via an outlet 1167A. The wet solids,left on cake side 1168, would be removed from housing 1162 via an outlet1168A.

Returning to FIG. 2, this illustrated process has three extraction units110A, 110B, 110C. Unit 110A has mixing tank 112A, pump 114A, mechanicalseparator 116A, and the piping to operably connect the elements. Unit110B has mixing tank 112B, pump 114B, mechanical separator 116B, and thepiping to operably connect the elements. Unit 110C has mixing tank 112C,pump 114C, mechanical separator 116C, and the piping to operably connectthe elements.

Beer feed 10 is fed into tank 112A where it is mixed with water/solventstream 31 (described later). This mixture, as stream 11, is pumped viapump 114A to mechanical separator 116A, where it is split intowater/solvent stream 30 and wet solids stream 34.

Wet solids stream 34 is fed into tank 112B where it is mixed withwater/solvent stream 32 (described later). This mixture, as stream 12,is pumped via pump 114B to mechanical separator 116B, where it is splitinto water/solvent stream 31 and wet solids stream 35.

Wet solids stream 35 is fed into tank 112C where it is mixed with firstsolvent stream 15. This mixture, as stream 13, is pumped via pump 114Cto mechanical separator 116C, where it is split into water/solventstream 32 and wet solids stream 20.

Stream 30, from unit 110A, is referred to as a “full miscella”. In theembodiment illustrated in FIG. 2, because there are three units, eachstream is allotted a third (i.e., ⅓) designation. Stream 31, from unit110B, is referred to as a “⅔ miscella” and stream 32, from unit 110C, isreferred to as a “⅓ miscella”. Full miscella stream 30 has a lowersolvent concentration and a higher water concentration than ⅔ miscellastream 31, which has a lower solvent concentration and a higher waterconcentration than ⅓ miscella stream 32.

Each of these streams 30, 31, 32 is reused in the process. Stream 31 isrecycled and fed into tank 112A, and stream 32 is recycled and fed intotank 112B. Full miscella stream 30, composed of water from beer feed 10and first solvent from stream 15, is used in ‘water-from-solvents’separation subprocess B. Wet solids stream 20, composed of solids andfirst solvent from stream 15, progresses to ‘solvent-from-solids’separation subprocess A.

‘Solvent-from-Solids’ Separation Subprocess A

Returning to FIG. 1, from water extraction system 100, wet solids stream20 is conveyed to ‘solvent-from-solids’ separation subprocess A. Insubprocess A, solvent from wet solids stream 20 is removed, by using asecond solvent, to obtain dry solid stream 90. Second solvent isintroduced to subprocess A as stream 70. First solvent (originally fromstream 15) and second solvent from stream 70 depart subprocess A asstream 80/230.

In subprocess A, the first solvent from stream 15, such as an alcohol,is extracted from the solids and replaced with a second solvent. Thesecond solvent is removed from the solids and dry solids are obtained.‘Solvent-from-solids’ separation subprocess A is generally configured astwo sub-subprocess, solvent extraction and thermal drying.

Referring to FIG. 4, ‘solvent-from-solids’ separation subprocess A isillustrated having solvent extraction system 200 and drying system 300.An alternate descriptive term for solvent extraction system 200 is asolvent extractor or a solid-liquid or solid-solvent extraction unit.Solvent extraction system 200 is configured to remove the first solventfrom wet solids stream 20 and replace the first solvent with a secondsolvent.

Solvent extraction system 200 transfers one or more components from wetsolids stream 20 into the extraction second solvent stream (describedbelow). Typically, solvent extraction system 200 operates in acounter-current arrangement.

In addition to wet solids stream 20 being fed into extraction system200, an extraction second solvent stream 70 is fed into system 200. Itis the solvent in stream 70 that will extract and replace the solventfrom wet solids 20. Second solvent from stream 70 combines with ordisplaces the first solvent from feed stream 15 in solids stream 20 asstream 20 and solvent stream 70 pass in system 200.

The second solvent is selected for stream 70 based on a lower heat ofvaporization or enthalpy of vaporization than the first solvent ofstream 15, which is present in wet solids stream 20. Preferably, thesolvent of stream 70 is soluble with and miscible with the first solventof stream 15. The solvent of stream 70 and the solvent of stream 15 mayor may not form an azeotropic mixture; if an azeotrope is not formed,subsequent separation of the solvents is more simple.

Examples of suitable solvents for stream 70 include ethers, (such asethyl ether, MTBE (methyl tert-butyl ether), ETBE (ethyl tert-butylether), fluorinated ethers, and other low molecular weight ethers),halogenated hydrocarbons (e.g., n-propyl bromide or 1-bromopropane,commercially available under the trade name “Hypersolve NPB”), straightchain low molecular hydrocarbons (such as hexane, pentane), and lowmolecular weight aromatic hydrocarbons (such as toluene, benzenes,xylenes), and any mixtures thereof.

The second solvent is selected on the basis of high solubility with thefirst solvent (e.g., ethanol), low solubility with water, and ease ofseparation between the first and second solvents, generally based ondifferential of heat of vaporization or enthalpy of vaporization.

Stream 70 may be provided by an external source, but is preferablyrecycled from the solvent removed from the solids, and from overheadstream 70 from still 700, as will be discussed below.

As stated above, first solvent from stream 15, now present in wet solidsstream 20, is replaced with second solvent from stream 70 by solventextraction system 200. The resulting output streams from system 200 arewet solids stream 220 and liquid stream 230; see FIG. 4. Solid stream220 is composed of the solids and an amount of second solvent fromstream 70. Wet solids stream 220 progresses to drying system 300, wherethe second solvent is removed from the solid.

Liquid stream 230 is generally composed of the solvent from solventstream 15 and second solvent from stream 70. Liquid stream 230progresses to and is treated by subprocess B, described below.

Solvent Extraction System 200

A preferred configuration for a solvent-solid extraction system 200 isillustrated in FIG. 5. As seen in FIG. 4 and in FIG. 5, wet solidsstream 20 and second solvent stream 70 enter system 200, and wet solidsstream 220 and liquid stream 230 exit system 200.

Solvent-solid extraction system 200 has at least one extraction unit210. In the system 200 illustrated in FIG. 5, system 210 has threeextraction units, specifically, 210A, 210B, 210C. Each extraction unit210 includes a mixing tank 212, a pump 214, mechanical separator 216,and the piping to operably connect the elements.

Mixing tank 212 can be any suitable receptacle for combining andtemporarily storing solid and liquid materials. In the embodimentillustrated, tank 212 accepts wet solids stream 20 and liquid stream 41,which will be described below. Examples of suitable materials for tank212 include steels, such as carbon steel and stainless steels.

A preferred material is 304 stainless steel. The volume of tank 212 isbased on the material flow volumes and desired residence time in tank212. A 30 gallon tank is a suitable size for some processes.

Pump 214, used to move material from tank 212, is positioned downstreamof tank 212. Pump 214 is selected for its ability to move the materialfrom tank 212, which includes solid material and liquid, to mechanicalseparator 216. Examples of suitable pumps include diaphragm pumps,centrifugal pumps, and pumps designed to pump a combination of liquidand solids. An example of a preferred pump 214 is a centrifugal pumpavailable from Goulds Pumps of ITT Industries.

Mechanical separator 216 separates solid material from liquid. Examplesof suitable mechanism separating equipment include Rotocel extractors,double screw extractors, baskets, rotary perforated belts, slidingrolls, and loop extractors; this equipment is well known forsolid/liquid extraction processes. The specific equipment used will bedependent on the solvents used in the process and in the solvent ratios.

Preferred equipment for use in extraction system 200 is a stationaryscreen, described below.

The piping connecting tank 212, pump 214, and mechanical separator 216,for each extraction unit 210, is selected for its ability to move thesolid-liquid material. An example of preferred piping is 1 inch carbonsteel piping.

A preferred configuration for a screen mechanical separator 216 isillustrated in FIG. 3A as separator 116; that is, mechanical separator216 can be the same as mechanical separator 116 from water extractionsystem 100.

Returning to FIG. 5, the illustrated process has three extraction units210A, 210B, 210C. Unit 210A has mixing tank 212A, pump 214A, mechanicalseparator 216A, and the piping to operably connect the elements. Unit210B has mixing tank 212B, pump 214B, mechanical separator 216B, and thepiping to operably connect the elements. Unit 210C has mixing tank 212C,pump 214C, mechanical separator 216C, and the piping to operably connectthe elements.

Wet solids stream 20 is fed into tank 212A where it is mixed with liquidstream 41 (described later). This mixture, as stream 21, is pumped viapump 214A to mechanical separator 216A, where it is split into liquidstream 230 and wet solids stream 44.

Wet solids stream 44 is fed into tank 212B where it is mixed with liquidstream 42 (described later). This mixture, as stream 22, is pumped viapump 214B to mechanical separator 216B, where it is split into liquidstream 41 and wet solids stream 45.

Wet solids stream 45 is fed into tank 212C where it is mixed with secondsolvent stream 70. This mixture, as stream 23, is pumped via pump 214Cto mechanical separator 216C, where it is split into liquid stream 42and wet solids stream 220.

Liquid stream 230, from unit 210A, is referred to as a “full miscella”.Stream 41, from unit 210B, is referred to as a “⅔ miscella” and stream42, from unit 210C, is referred to as a “⅓ miscella”. Full miscellastream 230 has a lower second solvent concentration and a higher firstsolvent concentration than ⅔ miscella stream 41, which has a lowersecond solvent concentration and a higher first solvent concentrationthan ⅓ miscella stream 42.

Each of these streams 230, 41, 42 is reused in the process. Stream 41 isrecycled and fed into tank 212A, and stream 42 is recycled and fed intotank 212B. Full miscella stream 230, composed of first solvent fromstream 15 and second solvent from stream 70, is used in‘water-from-solvents’ separation subprocess B. Wet solids stream 220,composed of solids and second solvent from stream 70, progresses todrying system 300.

Drying System 300

Wet solids stream 220, having solids and second solvent from stream 70,from solvent extraction system 200, is fed to drying system 300, wherethe solvent and any other volatile liquids or solvents are removed fromthe solids. Drying system 300 is the only unit in ‘solvent-from-solids’separation subprocess A that uses thermal energy. Examples of suitableequipment for drying system 300 include a steam-jacketed tube dryer(such as a Schnecken tube dryer), steam-heated-screw tube dryer, arotary dryer, a belt dryer, a down-draft desolventizer, or a DT; thisequipment is well known for drying processes. A preferred drying system300 includes a steam-jacketed tube style dryer.

The solvent is thermally removed from the solids at drying system 300,and dry solids are obtained as output stream 90. The second solventremoved exits drying system 300 as stream 80. Stream 80 may be furtherprocessed. In the process embodiment illustrated in FIG. 4, stream 80 iscombined with miscella stream 230 and sent to ‘water-from-solvents’separation subprocess B.

‘Water-from-Solvents’ Separation Subprocess B

Returning to FIG. 1, stream 30, composed of water from beer feed 10 andfirst solvent from stream 15, is conveyed to ‘water-from-solvents’separation subprocess B and processed to separate the water fromsolvent.

However, to maximize the separation to provide desired output streams,subprocess B preferably utilizes a second solvent, provided tosubprocess B as solvent stream 40.

Solvent of stream 40 is selected to have a lower heat of vaporization orenthalpy of vaporization than the components of stream 30, that is, thewater from feed stream 10 and the solvent of stream 15. In a preferredmethod, the solvent of stream 40 is the same as the solvent of stream70, from ‘solvent-from-solids’ separation subprocess A, described above.Preferably, solvent stream 40 is recycled from ‘solvent-from-solids’separation subprocess B; specifically, solvent stream 40 is obtainedfrom stream 80.

Stream 80 is combined with stream 230 and this combined stream 80/230 isfed as a single stream to subprocess B. Stream 40 is added as necessaryto assure a proper concentration of the three major components, water,first solvent and second solvent.

Any known methods can be used to separate the water from the solvent.Examples of suitable liquid-liquid extraction or liquid-liquidseparation methods include distillation, for example packed,York-Scheibel, Oldshue-Ruston, rotating disc, Karr or pulsed columns.Another suitable separation method is with a centrifugal contactor.

One general configuration for ‘water-from-solvents’ separation process Bis illustrated in FIG. 6. Subprocess B includes a liquid-liquidseparation unit 400 and two distillation units 500, 600.

In this embodiment, liquid stream 30, which enters liquid-liquid processunit 400 at the bottom, has a density less than stream 80/230 whichenters at the top of unit 400. Thus the components of stream 30 rise inunit 400 while components in stream 80/230 fall in the column. Exitingfrom unit 400 are top stream 45 from the top of unit 400 and a bottomstream 65 from the bottom of unit 400. The particular composition ofstreams 45, 65 will depend on the composition of streams 30 and 80/230.Stream 40 is a make-up stream to assure proper balance of water, firstsolvent and second solvent in unit 400.

There are components in each entering stream 30, 40 that are soluble inone another and some that are insoluble in each other. By choice, thesolvent of stream 80/230 and water are typically not soluble in eachother and form an upper and lower phase rich in one or the other. As thesolvent may have a density greater or lesser than that of water, thewater rich phase may be at the top or bottom. If the solvent of stream80/230 is assumed to have a density of 1.3, and therefore denser thanwater, the solvent rich phase will exit out the bottom of the column 400as stream 65 and the water-rich phase out the top as stream 45. Stream45 tends to be a stream high in alcohol and water with other lesserwater-soluble components, possibly with a small amount of the solvent ofstream 80/230. Stream 65 is a stream high in solvent, with possiblysmall amounts of alcohol and other components.

Stream 45 is sent to process unit 500, an evaporation or distillationdevice, for further separation into streams 55 and 60. Stream 65 is sentto process unit 600, a different distillation or evaporation device, forfurther separation into streams 50 and 75.

In many processes, streams 50, 55, 60, 75 are sufficiently pure so thatthe material from these streams can be sold or otherwise used withoutthe need for additional processing.

A Preferred Embodiment of the Process

A preferred embodiment of the process is diagrammatically illustrated inFIG. 7. This process has an initial extraction process that removes thewater from the solids followed by two subprocesses. The first subprocessremoves the initial solvent from the solids and a second subprocess thatseparates and reclaims the water, solvent and other components. Thedescription of this preferred process uses the same reference numeralsused before for like streams and equipment, as appropriate, except thatthe reference numerals are followed by an “a”.

In this embodiment of a preferred process, a beer stream 10 a (composedof corn solids, water, ethanol, oils, glycerol and other minorcomponents) is fed into a solid-liquid extraction system 100 a. Analternative term for solid-liquid extraction system 100 a is a waterextractor or water extraction unit. Water extraction system 100 a isdesigned to remove water from the feed stream 10 a and replace the waterwith a solvent. Examples of suitable solids-liquid extraction equipmenthave been described previously as water extraction system 100, and apreferred system 100 a includes three separators 116. Thewater-extraction system 100 a operates in a counter-current fashion.

A first solvent, an extraction solvent, 15 a is fed into waterextraction system 100 a where part of the solvent replaces the waterfrom stream 10 a. In this embodiment, the extraction solvent is ethanol.Ethanol has a lower heat of vaporization or enthalpy of vaporizationthan the water in feed stream 10 a.

System 100 a, the resulting output streams are wet solids stream 20 aand liquid stream 30 a. Solid stream 20 a progresses to and is treatedby ‘solvent-from-solids’ separation subprocess A, described below.Liquid stream 30 a progresses to and is treated by ‘water-from-solvents’separation subprocess B, also described below.

Subprocess A

Wet solids stream 20 a from system 100 a is pumped to solids-liquidextractor system 200 a by piping. Examples of suitable equipment forsystem 200 a have been provided previously as solids-liquid extractorsystem 200, and a preferred system 200 a includes three separators 216.Typically solvent extraction system 200 a operates in a counter-currentarrangement.

Also entering solvent extraction system 200 a is a second solvent,stream 70 a. In this embodiment, the solvent is n-propyl bromide.n-propyl bromide has a lower heat of vaporization or enthalpy ofvaporization than the water in feed stream 10 a and the ethanol ofstream 15 a.

In solvent extraction system 200 a, ethanol in stream 20 a, particularlythat in the interstitial spaces of the solids, is replaced with n-propylbromide from stream 70 a. The ethanol leaves system 200 a leave asstream 230 a and the solids, now wet with n-propyl bromide exit system200 a as stream 220 a.

Stream 220 a is fed to a dryer 300 a where n-propyl bromide and anyother remaining volatile liquids or solvents are removed from thesolids. Dryer 300 a is the only unit in subprocess A that uses thermalenergy. Examples of suitable equipment for dryer 300 a have beenpreviously described in respect to dryer 300. Dry solids exit as outputstream 90 a. The thermally removed solvent exits dryer 300 a as stream80 a, a vapor. Stream 80 a is combined with liquid stream 230 a. Thiscombined stream 80 a/230 a and stream 30 a is fed into liquid-liquidextraction unit 400 a in ‘water-from-solvents’ separation subprocess B.

Subprocess B

Combined stream 30 a is provided to the bottom of process unit 400 a. Asolvent stream 80 a/230 a enters at the top of unit 400 a. In thisembodiment, the solvent of stream 80 a/230 a is n-propyl bromide. Stream30 a has a density less than n-propyl bromide, which enters at the topof unit 400 a. Thus the components of stream 80 a/230 a fall in thecolumn while components in stream 30 a rise in the column. Normal-propylbromide, with a density of 1.3, will therefore exit out the bottom ofthe column as a solvent-rich stream 65 a, and the water-rich phase willexit out the top as stream 45 a.

Stream 45 a is high in alcohol and water content with other lesserwater-soluble components. There may be a small amount of n-propylbromide in stream 45 a.

Stream 45 a is sent to process unit 500 a, an evaporation ordistillation device. Unit 500 a separates the ethanol from the mixtureof stream 45 a; the ethanol, as a vapor and as an azeotrope of ethanoland water, leaves unit 500 a as stream 60 a. Stream 60 a may either becondensed, used as is, or sent for further processing to remove othercomponents. Stream 60 a may also be conveyed, as a vapor, to otherpurification devices to provide a product ethanol that is 99.9+% pure.

Stream 55 a from process unit 500 a is mostly water with some watersoluble components that did not vaporize in unit 500 a. This liquidstream 55 a may be used as is or further refined or purified.

Returning to unit 400 a, stream 65 a, the high organic bottom streamfrom unit 400 a, is also sent to a distillation or evaporation device.The majority of stream 65 a consists of n-propyl bromide and theremainder of stream 65 a is composed of fat soluble components, such ascorn oil. Stream 65 a feeds process device 600 a which has an exitingvapor stream 75 a and a liquid stream 50 a. Stream 75 a is primarilyn-propyl bromide. This vapor can be condensed and recycled (reused) inthe solid-liquid extraction subprocess A, as stream 70 a. The liquidstream 50 a is primarily fats and oils; this stream may be used as is ormay be further refined.

Alternate Embodiments of Process Using Sequential Solvents

A first alternate embodiment of the process is diagrammaticallyillustrated in FIG. 8. This process has an initial extraction processthat removes the water from the solids followed by two subprocesses. Thefirst subprocess removes the initial solvent from the solids and asecond subprocess that separates and reclaims the water, solvent andother components. The description of this preferred process uses thesame reference numerals used before for like streams and equipment, asappropriate, except that the reference numerals are followed by a “b”.

In this embodiment, feed stream 10 b is fed into a solid-liquidextraction system 100 b where the solids of feed stream 10 b areseparated from the water. Examples of suitable solids-liquid extractionequipment have been described previously as water extraction system 100,and a preferred system 100 b includes separators 116.

An extraction solvent stream 15 b is fed into water extraction system100 b with feed stream 10 b. In this embodiment, the extraction solventis ethanol. Ethanol has a lower heat of vaporization or enthalpy ofvaporization than the water in feed stream 10 b. The resulting outputstreams from system 100 b are wet solids stream 20 b and liquid stream30 b. Solid stream 20 b progresses to and is treated by‘solvent-from-solids’ separation subprocess A, described below. Liquidstream 30 b progresses to and is treated by ‘water-from-solvents’separation subprocess B, also described below.

Subprocess A

From water extraction system 100 b, solid stream 20 b is conveyed tosolid-liquid extraction system 200 b where the solvent from stream 15 bis removed from the solids and replaced with second solvent entering asstream 70 b. In this embodiment, the solvent is ethyl ether, which has alower heat of vaporization or enthalpy of vaporization that the water infeed stream 10 b and the ethanol of stream 15 b. The ethyl ether ofstream 70 b may be provided by an external source, but is preferablyrecycled from the solvent removed from the solids, and from overheadstream 75 b from still 600 b, as will be discussed below.

In solvent extraction system 200 b, ethanol in stream 20 b is replacedwith ethyl ether from stream 70 b. The ethanol leaves system 200 b asstream 230 b and the solids, now wet with ethyl ether, exit system 200 bas stream 220 b.

Stream 220 b is fed to a dryer 300 b where ethyl ether and any otherremaining volatile liquids or solvents are removed from the solids. Thethermally removed solvent exits dryer 300 b as stream 80 b, a vapor, andprogresses to condenser 800. Depending on the volume of stream 80 b, aportion of it may be removed as an ether side-stream. The remainder ofstream 80 b is returned to system 200 b.

Stream 230 b progresses to ‘water-from-solvents’ separation subprocessB.

Subprocess B

‘Water-from-solvents’ separation subprocess B treats liquid stream 30 bfrom water extraction system 100 b and stream 230 b from subprocess A.Stream 30 b is provided to the top of process unit 400 b. Liquid-liquidextraction unit 400 b is typically a tall column with four ports, oneinlet at the top and one inlet at the bottom, and two outlets, one atthe top and one at the bottom; streams from the two inlets runcounter-current. A solvent stream 40 b enters at the bottom of unit 400b. In this embodiment, the solvent of stream 40 b is ethyl ether. Thusthe components of stream 40 b rise in the column while components instream 30 b fall in unit 400 b, resulting in exiting aqueous bottom exitstream 45 b, which has a lower concentration of ethanol than stream 30 bdid at the inlet, having transferred some ethanol to the ether stream.Also exiting is top exit stream 65 b, mostly ether but which has ahigher concentration of ethanol than stream 40 b did at the inlet,having received some ethanol from stream 30 b.

Bottom exit stream 45 b is composed of the water, ethanol, and someother hydrocarbons from feed stream 10 b, and a small amount of ethylether from stream 40 b. Stream 45 b is fed into a still 500 b, wherethermal energy is used to separate all volatile components from waterand provide an overhead stream 60 b and a bottoms stream 55 b. Still 500b is one of only two process elements, in this embodiment of subprocessB, that utilizes thermal energy.

Overhead stream 60 b includes ethanol and any trace amount of ether thatmay have been present in stream 45 b. Bottom stream 55 b includes waterand any other heavy materials. A generally small amount of external heator energy is needed to provide the separation, due to the differentboiling points of water and solvents.

Overhead stream 60 b progresses to a condenser 700, where ethanol vaporsare condensed to liquid. The resulting liquid stream is fairly pure,typically at least 90% and preferably at least 95%. The ethanol can becollected and used for solvent stream 15 b. Bottoms stream 55 b isgenerally sufficiently pure water to allow disposal with a minimum offurther purification.

Top exit stream 65 b from liquid-liquid extraction unit 400 b containsthe majority of ether from unit 400 b, a major amount of ethanol fromstream 30 b, and typically includes a small amount of water. Top exitstream 65 b and stream 230 b are fed into a still 600 b, the second ofthe two process elements of subprocess B in this embodiment thatutilizes thermal energy. Top exit stream 65 b is separated by still 600b into an overhead stream 75 b and a bottoms stream 67.

Overhead stream 75 b includes the ether; typically this stream is fairlypure, typically at least 95% pure and preferably at least 98% pure.Overhead stream 75 b is recycled into the process and combined withether stream 80 b, out from dryer 300 b of subprocess A.

Bottom stream 67 includes the heavier ethanol; this stream is fairlypure, typically at least 90% pure and preferably at least 95% pure.Bottom stream 67, composed of fairly pure ethanol, can be treated in thesame manner as stream 60 b, either collected, returned to the process assolvent stream 15 b, or further purified.

A second alternate embodiment of the process using two sequentiallyapplied solvents is diagrammatically illustrated in FIG. 9. This processhas an initial extraction process that removes the water from the solidsfollowed by two subprocesses. The first subprocess removes the initialsolvent from the solids and a second subprocess that separates andreclaims the water, solvent and other components. The description ofthis preferred process uses the same reference numerals used before forlike streams and equipment, as appropriate, except that the referencenumerals are followed by a “c”.

FIG. 9 shows a process similar to the process of FIG. 8, except thisembodiment includes additional process equipment. Bottom stream 67 cfrom unit 600 c is sent to an evaporator unit 900, which is designed toboil off an azeotropic mixture of ethanol and water, to provide stream76 and stream 77. Stream 76 contains a mixture of ethanol, waterpreferably and some small amounts of additional volatile material.Stream 76 progresses to system 1000, a series of molecular sieves.System 1000 takes the azeotropic mixture from evaporator unit 900 andprovides ethanol, stream 78. Remaining water from the separation leavessystem 1000 as stream 79.

The nonvolatilized portion of stream 75 c exits unit 900 as stream 77,relatively clean water.

A third alternate embodiment of the process using two sequentialsolvents is diagrammatically illustrated in FIG. 10. The description ofthis preferred process uses the same reference numerals used before forlike streams and equipment, as appropriate, except that the referencenumerals are followed by a “d”.

FIG. 10 is another embodiment of the process and is similar to theprocess of FIG. 9. However, the process of FIG. 10 has an addedliquid/liquid extractor unit 450. Unlike the embodiments of FIGS. 8 and9, the aqueous (bottom) stream 45 d, from unit 400 d does not feed unit500 d directly, but instead is one of two feed streams to unit 450.Similar to unit 400 d, unit 450 extracts ethanol from an aqueous feedstream using an ether, which is the other feed stream 46 provided tounit 450. The organic (top) phase stream from unit 450, stream 47 iscombined with organic phase stream 65 d from unit 400 d. Additionally,vapor stream 60 d from unit 500 d is not sent to a condenser but insteadis combined with streams 47 and 65 d and the resulting stream iscombined with stream 230 d from system 200 d. This combined stream isfed to unit 600 d. Also in this embodiment, stream 67 d is split intostreams 61 and 62. Stream 62 carries the appropriate amount of ethanolto provide 200-proof ethanol and ethanol to regenerate the sieve beds ofsystem 1000. Stream 61 is sent to a storage tank for reuse in theprocess.

Alternate embodiments, of any of the process described above, whichutilize an initial extraction process that removes the water from thesolids followed by two subprocesses, are within the scope of thisinvention.

The various processes described above used two solvents sequentially, orstep-wise, to remove water from solids; specifically, the first solventreplaced the water, and then the second solvent replaced the firstsolvent. Although the description above labeled solvents as “firstsolvents” and “second solvents”, and the like, it should be recognizedthat these groupings are not limiting. In some designs, for example, asolvent listed in the “second solvent” group may be used as a firstsolvent; similarly, a solvent listed in the “first solvent” group may beused as a second solvent. The only basis is that the second solvent hasa heat of vaporization, enthalpy of vaporization, or other such physicalproperty, that is less than that of the first solvent. If a thirdsolvent is used, the third solvent would have a heat of vaporization,enthalpy of vaporization, or other such physical property, that is lessthan that of the second solvent.

General Operating Conditions

The following generally operating conditions are suitable for theprocess according to the invention, when operated in a typical pilotplant scale.

Stream Flowrate Feed stream 10 100-120 lbs/min (15-25 gal/min) Firstsolvent stream 15 Based on stream 10 Solids stream 20 Based on streams10 and 15, and on stream 70 Second solvent stream 70 Based on stream 20

$\begin{matrix}{{\frac{{First}\mspace{14mu}{solvent}\mspace{14mu}{stream}\mspace{11mu} 15\mspace{11mu}\left( {{lb}\text{/}\min} \right)}{{{Feed}\mspace{11mu}{Stream}\mspace{11mu} 10\mspace{11mu}\left( {{lb}\text{/}\min} \right)}\;} = {{about}\mspace{11mu} 1.0\mspace{14mu}{to}\mspace{11mu} 0.3}}\;} & (I) \\{{\frac{{Second}\mspace{14mu}{solvent}\mspace{14mu}{stream}\mspace{11mu} 70\mspace{11mu}\left( {{lb}\text{/}\min} \right)}{{{Solids}\mspace{11mu}{s{tream}}\mspace{11mu} 20\mspace{11mu}\left( {{lb}\text{/}\min} \right)}\;} = {{about}\mspace{11mu} 1.1\mspace{14mu}{to}\mspace{11mu} 0.3}}\text{}\;{{{Process}\mspace{14mu}{temperature}} = {{85\text{-}90{^\circ}\mspace{14mu}{F.{Process}}\mspace{14mu}{pressure}} = {atomospheric}}}} & ({II})\end{matrix}$

The flow rates within the system that are useful in accordance with theinvention are indicated above. Generally, feed stream 10 has a flow rateof 100 to 120 lbs/min. The flow rate of first solvent stream 15 is setin accordance with equation (I). The flow rates of second solvent stream70 generally range from 10-20 lbs/min, but may also be adjusted relativeto stream 20 through equation (II). The flow rates of the variousstreams into and out from subprocess B are generally governed by streamflow rates in system 100 and subprocess A.

Exemplary Process Conditions

Provided below are exemplary stream components and proposed materialflow rates for a commercial size, modeled process, described inreference to FIG. 7, which used n-propyl bromide as the subsequentsecond solvent. A binary diagram, for n-propyl bromide/ethanol/water isprovided as FIG. 11. It was found that using n-propyl bromide, for asystem desirous of separating water and ethanol, was beneficial in thatthere was a tendency for the system to equilbriate at a low waterpercentage.

Solids Feed Stream Ethanol Feed Stream 10a 15a Flow Rate 4000 lb/min1090 lb/min Fiber 12 wt-% 0 Oil Trace 0 Water 73 wt-%  7.4 wt-% GlycerolTrace 0 Acetic Acid Trace 0 Ethanol 13 wt-% 92.6 wt-%

In unit 100 a, feed stream 10 a (usually at a temperature of about85-90° F.) and first solvent stream 15 a would be sent through a seriesof six screen extractor units 116 (see FIG. 2, where a series of threescreen extractor units 116A, 116B, 116C are illustrated). The resultingstreams from the six extractors would be:

Flow Rate Water Ethanol Fiber Extractor #1 3543 lb/min 70 wt-% 17 wt-%11 wt-% solids stream Extractor #2 3216 lb/min 65 wt-% 21 wt-% 12 wt-%solids stream Extractor #3 2889 lb/min 58 wt-% 27 wt-% 14 wt-% solidsstream Extractor #4 2562 lb/min 50 wt-% 33 wt-% 15 wt-% solids streamExtractor #5 2234 lb/min 40 wt-% 42 wt-% 17 wt-% solids stream Extractor#6 1906 lb/min 26 wt-% 53 wt-% 20 wt-% solids stream Wet Solids StreamAqueous Stream 20a 30a Flow Rate 1906 lb/min 3251 lb/min Fiber 20 wt-% 3 wt-% Oil Trace 0 Water 26 wt-% 78 wt-% Glycerol Trace 0 Acetic AcidTrace 0 Ethanol 53 wt-% 19 wt-%

Wet solids stream 20 a would progress to unit 200 a, where it and secondsolvent stream 70 a would be sent through a series of six screenextractor units 216 (see FIG. 5, where a series of three screenextractor units 216A, 216B, 216C are illustrated). The resulting streamsfrom the six extractors would be:

Flow Rate Water Ethanol n-PB Fiber Extractor 1799 lb/min 23 wt-% 49 wt-% 6 wt-% 22 wt-% #1 solids stream Extractor 1691 lb/min 21 wt-% 44 wt-%12 wt-% 23 wt-% #2 solids stream Extractor 1583 lb/min 18 wt-% 38 wt-%20 wt-% 25 wt-% #3 solids stream Extractor 1475 lb/min 14 wt-% 31 wt-%29 wt-% 26 wt-% #4 solids stream Extractor 1368 lb/min 10 wt-% 23 wt-%38 wt-% 28 wt-% #5 solids stream Extractor 1260 lb/min  6 wt-% 13 wt-%50 wt-% 31 wt-% #6 solids stream

The miscella stream from Extractor #1 would correspond to stream 230 aof FIG. 7. The components of stream 230 a are provided below.

The solid stream obtained from Extractor #6 would correspond to stream220 a of FIG. 7. Stream 220 a, fed into dryer 300 a, provides solidsstream 90 a and vapor stream 80 a. Solids stream 90 a would be a flow of389 lb/min of 100% solids

Vapor stream Miscella stream Combined Stream 80a 230a 80a/230a Flow Rate871 lb/min 1410 lb/min 2281 lb/min Water  8 wt-% 30 wt-% 21 wt-% Ethanol19 wt-% 62 wt-% 46 wt-% n-PB 72 wt-%  7 wt-% 32 wt-%

Combined stream 80 a/230 a would be fed into the top of separationcolumn 400 a and aqueous stream 30 a would be fed into the bottom ofcolumn 400 a and streams 45 a and 65 a would exit. In this example, noadditional solvent, as stream 40 a, was added.

Top Organic Aqueous Bottom Stream 45a Stream 65a Flow Rate 655 lb/min4877 lb/min Water 1 wt-% 61 wt-%  Ethanol 2 wt-% 34 wt-%  n-PB 93 wt-% 3 wt-% Oils 4 wt-% 0 wt-% Fiber/solids 0 wt-% 2 wt-%

Stream 45 a would be fed to still 500 a and the exiting streams 60 a, 55a would have the compositions listed below. In this example, a steamsparge stream, at 35 lb/min, was added to carry or otherwise facilitatetransporting the solvents to the top of the still. Stream 65 a would befed to still 600 a and the exiting streams 75 a, 50 a would have thecompositions listed below. In this example, heat exchangers would beused for flashing steam 65 a prior to entering still 600 a; this woulddecrease the entering mass flow rate to about 4700 lb/min.

Vapor Ethanol Water Stream Oil Recovery Recovery Stream 60a Stream 55a75a 50a Flow Rate 665 lb/min 25 lb/min 1706 lb/min 3003 lb/min Water 6wt-% 0.6 wt-%   6 wt-% 95 wt-%  Ethanol 2 wt-% 0 wt-% 92 wt-%  0 wt-%n-PB 92 wt-%  0 wt-% 2 wt-% 0 wt-% Oils/glycerine 0 wt-% 99.3 wt-%   0wt-% 2 wt-% Fiber/solids 0 wt-% 0 wt-% 0 wt-% 3 wt-%

Additional Exemplary Process Conditions

Provided below are exemplary stream components and proposed materialflow rates for a modeled process described in reference to FIG. 10,which used ether as the second solvent.

Solids Feed Ethanol Feed Stream 10d Stream 15d Component wt-% lb/minwt-% lb/min Fiber 12.2 398.2 0 0 Oil 0.6 19.6 0 0 Water 69.9 2281.5 4.588.1 Glycerol 1.2 39.2 0 0 Acetic Acid 0.1 3.3 0 0 Ethanol 16.0 522.282.8 1621.6 Ether 0 0 12.7 248.7 Total 100 3264 100 1958.4 Wet SolidsAqueous Stream 20d Stream 30d Component wt-% lb/min wt-% lb/min Fiber44.1 394.2 0.1 4.0 Oil 1.1 9.8 0.2 9.8 Water 10.6 94.8 52.6 2274.9Glycerol 2.2 19.6 0.5 19.6 Acetic Acid 0 0 0.1 3.2 Ethanol 36.5 326.442.0 1817.4 Ether 5.6 50.1 4.6 198.7 Total 100 894.9 100 4327.5 EtherFeed Ether Feed Stream 40d Stream 70d Component wt-% lb/min wt-% lb/minFiber 0 0 0 0 Oil 0 0 0 0 Water 0 0 0 0 Glycerol 0 0 0 0 Acetic Acid 0 00 0 Ethanol 3.0 120.5 3.0 26.8 Ether 97.0 3894.7 97.0 868.1 Total 1004015.2 100 894.9 Wet Solids Liquid Stream 220d Stream 230d Componentwt-% lb/min wt-% lb/min Fiber 46.9 390.3 0.4 3.9 Oil 0.0 0.2 1.0 9.6Water 5.7 47.4 4.9 47.4 Glycerol 0.0 0.4 2.0 19.2 Acetic Acid 0.0 0.00.0 0.0 Ethanol 0.4 3.3 36.5 350.0 Ether 46.9 390.3 55.1 527.8 Total 100831.8 100 958.0 Dried Solids Ether Solvent Stream 90d Stream 80dComponent wt-% lb/min wt-% lb/min Fiber 89.0 390.3 0 0 Oil 0 0.2 0 0Water 10.8 47.4 0 0 Glycerol 0.1 0.4 0 0 Acetic Acid 0 0 0 0 Ethanol 0 00.8 3.3 Ether 0 0.4 99.2 389.9 Total 100 438.7 100 393.2 Bottoms TopStream 45d Stream 65d Component wt-% lb/min wt-% lb/min Fiber 0 0 0.14.0 Oil 0 0 0.2 9.8 Water 79.5 2274.9 0 0 Glycerol 0.7 19.6 0 0 AceticAcid 0.1 3.2 0 0 Ethanol 18.4 527.0 25.7 1410.8 Ether 1.2 35.1 74.04058.3 Total 100 2859.8 100 5482.9 Ethanol Water Stream 60d Stream 55dComponent wt-% lb/min wt-% lb/min Fiber 0 0 0 0 Oil 0 0 0 0 Water 5.027.7 99.0 2247.1 Glycerol 0 0 0.9 19.6 Acetic Acid 0 0 0.1 3.2 Ethanol95.0 527.0 0 0 Ether 0.0 0.0 0 0 Total 100 554.8 100 2270.0 EtherProduct Ethanol Stream 75d Stream 67d Component wt-% lb/min wt-% lb/minFiber 0 0 0.4 7.9 Oil 0 0 1.1 19.4 Water 0.1 2.4 2.5 40.0 Glycerol 0 01.1 19.2 Acetic Acid 0 0 0 0 Ethanol 1.0 46.3 94.9 1714.5 Ether 99.04585.7 0 0.5 Total 100 4634.5 100 1806.4

Only three pieces of the process equipment from the system depicted inand described with reference to FIG. 10 use thermal energy. Dryer 1300,which is a Schnecken tube-type dryer, uses an exemplary 77.3 lb/min ofsteam, still 1700 uses an exemplary 6532 lb/min of steam, and waterseparator 1500 uses an exemplary 199.5 lb/min of steam.

The above description has been, in most part, directed to processeswhere the two solvents are applied sequentially to the solids; that is,the solids are contacted with a first solvent and then with a secondsolvent. It is understood that, in accordance with the presentinvention, the two, or more, solvents can be simultaneously applied tothe solids; for example, multiple solvents can be mixed together priorto contacting the solids.

The solvents for concurrent or simultaneous application to the solidscan be similar to those discussed above. The first solvent is preferablysoluble in water but does not form an azeotropic mixture with water. Thesecond solvent is preferably soluble with the first solvent butinsoluble with water. The second solvent may, however, be miscible withthe first solvent, and/or with water. Additionally, the first solventhas a lower heat of vaporization and boiling point than water, and thesecond solvent has a lower heat of vaporization and boiling point thanthe first solvent. Generally, the same solvents can be used for a mixedon concurrent system as for a sequential or stepped system.

Examples of suitable solvents, that can be mixed, include alcohols (suchas ethanol, methanol, isopropyl alcohol, and gasohol), ketones (such asacetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK)),hydrocarbons, and any mixtures thereof. Examples of suitablehydrocarbons include ethers, (such as ethyl ether, MTBE (methyltert-butyl ether), ETBE (ethyl tert-butyl ether), fluorinated ethers,and other low molecular weight ethers), halogenated hydrocarbons (e.g.,n-propyl bromide or 1-bromopropane), straight chain low molecularhydrocarbons (such as hexane, pentane), and low molecular weightaromatic hydrocarbons (such as toluene, benzenes, xylenes), and anymixtures thereof.

The ratio of the solvents is selected based on the solvents, thematerial present in the solids (e.g., ethanol and water), and otherparameters. Suitable ratios are 1/99 to 99/1, 10/90 to 90/10, 25/75 to75/25, 30/70 and 70/30, and another ratio; as stated, the ratio isselected based on the solvents and the desired resulting properties,including separation effectiveness, cost of solvents, cost of separationof solvents or separation of solvents from solids, toxicity of solvents,etc. For example, for removal of water and ethanol from solids, ethanoland n-PB is one example of a preferred solvent combination; ethanol andhexane is another example. Examples of suitable solvent mixturesinclude: 84/16, 75/25, 67/33 and 50/50 weight ratios of n-PB/ethanol;84/16 is the azeotropic level. Based on numerous properties, includingeffectiveness of extraction, easy of separation, and cost, ratios of75/25 and 67/33 are preferred. Other suitable examples of solventmixtures include 79/21 hexane/ethanol, with is the azeotropic level.

The combined solvents work in generally the same manner as sequentialsolvents. Using an example of ethanol and n-PB on solids wet with waterand ethanol, the ethanol solvent combines with the water in theinterstitial spaces of the solids, for ethanol has a preference forwater over n-PB (at least partially due to ethanol being soluble inwater, and ethanol and n-PB not being soluble in one another). The n-PBreplaces the ethanol in those spaces and drags the ethanol and water outof those spaces. The used solvent stream (i.e., the n-PB, ethanol,water, with any other ingredients) can then be removed from the solidsby liquid-solid separation techniques, including filtering, decanting,and the like. In preferred systems, the used solid stream phaseseparates, with the n-PB separating from the ethanol and water. Smallamounts of solids may be entrained in either solvent, or present as alayer on either side or, or between, the solvents. Liquid-liquidextraction, including distillation, could be done on the used solventstream to separate the solvents. Any residual solvent (e.g., n-PB and/orethanol) can be removed from the solids, for example, by heating.

This discussion has been a brief summary of using multiple combinedsolvents to remove water from solids. Alternate embodiments are withinthe scope of this invention. The process described above used twosolvents concurrently, or mixed, to remove water from solids;specifically, the first solvent replaced the water, and then the secondsolvent replaced the first solvent, although in a single action.Although the description above labeled solvents as “first solvents” and“second solvents”, it should be recognized that these groupings are notlimiting. The only basis is that the second solvent has a heat ofvaporization, enthalpy of vaporization, or other such physical property,that is less than that of the first solvent. If a third solvent is used,the third solvent would have a heat of vaporization, enthalpy ofvaporization, or other such physical property, that is less than that ofthe second solvent.

The above specifications provide a complete description of the process,equipment, and compositions of the invention. Since many embodiments ofthe invention can be made without departing from the spirit and scope ofthe invention, the invention resides in the claims hereinafter appended.

1. A process for drying solids initially wet with water, the processcomprising: (a) contacting a feed stream from a fermentation processwith a first solvent and a second solvent, the feed stream comprisingsolids having interstitial spaces therebetween and water present in theinterstitial spaces and water absorbed by the solids, the first solventhaving a heat of vaporization lower than the heat of vaporization ofwater and being soluble with water, and the second solvent having a heatof vaporization lower than the heat of vaporization of the first solventand being miscible with the first solvent; (b) displacing the waterpresent in the interstitial spaces with the first solvent to providesolids having the first solvent in the interstitial spaces; and (c)displacing the first solvent present in the interstitial spaces with thesecond solvent to provide solids having the second solvent in theinterstitial spaces.
 2. The process according to claim 1, furthercomprising the step of: (e) removing the second solvent from theinterstitial spaces of the solids by the application of heat.
 3. Theprocess according to claim 1, wherein contacting a feed stream with afirst solvent comprises: (a) contacting the feed stream with a firstsolvent that is an alcohol.
 4. The process according to claim 3, whereincontacting a feed stream with a first solvent that is an alcoholcomprises: (a) contacting the feed stream with a first solvent that isethanol.
 5. The process according to claim 3, wherein the contacting thefeed stream with a second solvent comprises: (a) contacting the feedstream with a second solvent that is a halogenated hydrocarbon.
 6. Theprocess according to claim 5, wherein contacting the feed stream with asecond solvent comprises: (a) contacting the feed stream with a secondsolvent that is n-propyl bromide.
 7. The process according to claim 1,wherein contacting a feed stream with a first solvent and a secondsolvent comprises: (a) contacting the feed stream with the first solventand then contacting the feed stream with the second solvent.
 8. Theprocess according to claim 7, wherein: (a) contacting a feed stream witha first solvent comprises contacting a feed stream with an alcohol; (b)contacting the feed stream with a second solvent comprises contactingthe feed stream with n-propyl bromide; and the process furthercomprises: (c) obtaining a product that is at least 95% pure n-propylbromide; and (d) obtaining an alcohol product that is at least 90% purealcohol.
 9. The process according to claim 8, wherein: (a) contacting afeed stream with an alcohol comprises contacting with ethanol; and (b)obtaining an alcohol product that is at least 90% pure alcohol comprisesobtaining an alcohol product that is at least 95% pure ethanol.
 10. Theprocess according to claim 1, wherein contacting a feed stream with afirst solvent and a second solvent comprises: (a) contacting the feedstream with the first solvent combined with the second solvent.
 11. Theprocess according to claim 10, wherein: (a) contacting a feed streamwith a first solvent and a second solvent comprises combining a feedstream with an alcohol and with n-propyl bromide; and the processfurther comprises: (b) obtaining a product that is at least 95% puren-propyl bromide; and (c) obtaining an alcohol product that is at least90% pure alcohol.
 12. The process according to claim 11, wherein: (a)combining a feed stream with an alcohol comprises combining withethanol; and (b) obtaining an alcohol product that is at least 90% purealcohol comprises obtaining an alcohol product that is at least 95% pureethanol.